Novel corrosion inhibiting thermoplastic alloys can be prepared by blending corrosion inhibitors with selected plastics suitable for injection molding. In accordance with the present invention, thermoplastic alloys suited to form improved molded housings useful for protective enclosures for electronic media devices against corrosion. Certain thermoplastic substances are blended with selected corrosion inhibitors to create working formulations of these alloys which are adaptable for molding operations. The selected corrosion inhibitors are retained in-situ during the molding operation or cycle and yet will subsequently slowly vaporize and/or sublime into the device enveloping enclosures to provide protection for long term use and storage.
Flexible films incorporating vapor corrosion inhibitor chemicals have been available and are used widely for the protection of metallic articles in storage and shipping. Such applications are especially useful for sensitive electronic media devices and other delicate metallic articles. Paper has been coated with vapor corrosion inhibitors and used for protection of metallic articles during storage and shipping. Vapor corrosion chemicals are also available in small pellets and packages, and may be impregnated into plastic foam to provide other methods of protection. Vapor corrosion inhibitors may also be coated on paper and otherwise included in low melting flexible films such as polyethylene. All of the above methods are typically temporary in nature with the exception of appropriately packaged chemicals that can provide up to two years protection in enclosed or confined areas.
The most effective inhibitors volatilize easily and this volatility feature has been found to preclude their use in the higher melting thermoplastic systems which may be needed for some rigid enclosures. Acrylonitrile butadiene styrene (ABS) resins however are thermoplastic materials that provide an excellent balance of physical properties including impact and heat resistance and are suitable for many applications. In addition, ABS can be processed at a low enough temperature to enable the addition of a sufficient quantity of certain selected corrosion inhibitor chemicals to function effectively in protecting the metals intended to be enclosed in molded parts. The improved corrosion inhibiting formulations, in combination with the preselected ABS resins, provide a unique feature inasmuch as the corrosion inhibitors become semi-permanently encapsulated within the resin matrix, and thereafter leach out at a rate which provides ongoing protection over an extended period of time.